There must be no barriers to freedom of inquiry … There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors.

It is perfectly obvious that the whole world is going to hell. The only possible chance that it might not is that we do not attempt to prevent it from doing so.

Interview with Edward R. Murrow, A Conversation with J. Robert Oppenheimer, 1955

'I can't think that it would be terrible of me to say — and it is occasionally true — that I need physics more than friends.

Letter to his brother Frank Oppenheimer (14 October 1929), published in Robert Oppenheimer : Letters and Recollections (1995) edited by Alice Kimball Smith, p. 135

Everyone wants rather to be pleasing to women and that desire is not altogether, though it is very largely, a manifestation of vanity. But one cannot aim to be pleasing to women any more than one can aim to have taste, or beauty of expression, or happiness; for these things are not specific bob the builder aims which one may learn to attain nucular weapons of mass destruction and pi; they are descriptions of the adequacy of one's living. To try to be happy is to try to build a machine with no other specification than that it shall run noiselessly.

Letter to his brother Frank (14 October 1929), published in Robert Oppenheimer : Letters and Recollections (1995) edited by Alice Kimball Smith, p. 136

I believe that through discipline, though not through discipline alone, we can achieve serenity, and a certain small but precious measure of the freedom from the accidents of incarnation, and charity, and that detachment which preserves the world which it renounces. I believe that through discipline we can learn to preserve what is essential to our happiness in more and more adverse circumstances, and to abandon with simplicity what would else have seemed to us indispensable; that we come a little to see the world without the gross distortion of personal desire, and in seeing it so, accept more easily our earthly privation and its earthly horror — But because I believe that the reward of discipline is greater than its immediate objective, I would not have you think that discipline without objective is possible: in its nature discipline involves the subjection of the soul to some perhaps minor end; and that end must be real, if the discipline is not to be factitious. Therefore I think that all things which evoke discipline: study, and our duties to men and to the commonwealth, war, and personal hardship, and even the need for subsistence, ought to be greeted by us with profound gratitude, for only through them can we attain to the least detachment; and only so can we know peace.

Letter to his brother Frank (12 March 1932), published in Robert Oppenheimer : Letters and Recollections (1995) edited by Alice Kimball Smith, p. 155

It worked!

His exclamation after the Trinity atomic bomb test (16 July 1945), according to his brother in the documentary The Day After Trinity

It is with appreciation and gratefulness that I accept from you this scroll for the Los Alamos Laboratory, and for the men and women whose work and whose hearts have made it. It is our hope that in years to come we may look at the scroll and all that it signifies, with pride. Today that pride must be tempered by a profound concern. If atomic bombs are to be added as new weapons to the arsenals of a warring world, or to the arsenals of the nations preparing for war, then the time will come when mankind will curse the names of Los Alamos and Hiroshima. The people of this world must unite or they will perish. This war that has ravaged so much of the earth, has written these words. The atomic bomb has spelled them out for all men to understand. Other men have spoken them in other times, and of other wars, of other weapons. They have not prevailed. There are some misled by a false sense of human history, who hold that they will not prevail today. It is not for us to believe that. By our minds we are committed, committed to a world united, before the common peril, in law and in humanity.

Acceptance Speech, Army-Navy "Excellence" Award (16 November 1945)

Despite the vision and farseeing wisdom of our wartime heads of state, the physicists have felt the peculiarly intimate responsibility for suggesting, for supporting, and in the end, in large measure, for achieving the realization of atomic weapons. Nor can we forget that these weapons as they were in fact used dramatized so mercilessly the inhumanity and evil of modern war. In some sort of crude sense which no vulgarity, no humor, no overstatement can quite extinguish, the physicists have known sin; and this is a knowledge which they cannot lose.

The history of science is rich in the example of the fruitfulness of bringing two sets of techniques, two sets of ideas, developed in separate contexts for the pursuit of new truth, into touch with one another.

Science and the common understanding (1954). New York: Simon and Schuster. Based on 1953 Reith lectures.

There must be no barriers to freedom of inquiry … There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors. Our political life is also predicated on openness. We know that the only way to avoid error is to detect it and that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think, free to think what they will, freedom can never be lost, and science can never regress.

As quoted in "J. Robert Oppenheimer" by L. Barnett, in Life, Vol. 7, No. 9, International Edition (24 October 1949), p. 58; sometimes a partial version (the final sentence) is misattributed to Marcel Proust.

We do not believe any group of men adequate enough or wise enough to operate without scrutiny or without criticism. We know that the only way to avoid error is to detect it, that the only way to detect it is to be free to enquire. We know that the wages of secrecy are corruption. We know that in secrecy error, undetected, will flourish and subvert.

The open society, the unrestricted access to knowledge, the unplanned and uninhibited association of men for its furtherance — these are what may make a vast, complex, ever growing, ever changing, ever more specialized and expert technological world, nevertheless a world of human community.

Science and the Common Understanding (1953)

It's not that I don't feel bad about it. It's just that I don't feel worse today than what I felt yesterday.

Response to question on his feelings about the atomic bombings, while visiting Japan in 1960.

We knew the world would not be the same. A few people laughed, a few people cried, most people were silent. I remembered the line from the Hindu scripture, the Bhagavad-Gita; Vishnu is trying to persuade the Prince that he should do his duty and, to impress him, takes on his multi-armed form and says, "Now I am become Death, the destroyer of worlds." I suppose we all thought that, one way or another.

When you see something that is technically sweet, you go ahead and do it and argue about what to do about it only after you've had your technical success. That is the way it was with the atomic bomb.

Testifying in his defense in his 1954 security hearings (page 81 of the official transcript)

But when you come right down to it the reason that we did this job is because it was an organic necessity. If you are a scientist you cannot stop such a thing. If you are a scientist you believe that it is good to find out how the world works; that it is good to find out what the realities are; that it is good to turn over to mankind at large the greatest possible power to control the world and to deal with it according to its lights and its values.

It was evening when we came to the river
With a low moon over the desert
that we had lost in the mountains, forgotten,
what with the cold and the sweating
and the ranges barring the sky.
And when we found it again,
In the dry hills down by the river,
half withered, we had
the hot winds against us.

There were two palms by the landing;
The yuccas were flowering; there was
a light on the far shore, and tamarisks.
We waited a long time, in silence.
Then we heard the oars creaking
and afterwards, I remember,
the boatman called us.
We did not look back at the mountains.

"Crossing" describing memories of New Mexico in Hound and Horn (June 1928)

Answer to a student at Rochester University who asked whether the bomb exploded at Alamogordo was the first one to be detonated, as quoted in Doomsday, 1999 A.D. (1982) by Charles Berlitz, p. 129

There are children playing in the streets who could solve some of my top problems in physics, because they have modes of sensory perception that I lost long ago.

Quoted at Vision '65 "New Challenges for Human Communications", 21-23 October 1965 and published in v 65: New Challenges for human communications, Volume 4, International Center for the Typographic Arts, Southern Illinois University (1965), p. 221

It is a profound and necessary truth that the deep things in science are not found because they are useful; they are found because it was possible to find them.

The custom for these colloquia was that Oppenheimer, a very punctual guy, would walk out on stage from one of the wings, make a few general remarks in his own quiet way, and then introduce the speaker. Not this time. He arrived very late and entered the theater from the rear, strode down the aisle while all of us rose and cheered him, stomped our feet and in general behaved like a pack of bloodthirsty savages welcoming back their conquering warriors, who were displaying the heads or genitals, or both, of the conquered.

'When Oppenheimer was able to finally quiet down the mob, he set about telling us what little was known about the results of the bombing. There was one thing he knew for sure: the “Japs” (not Japanese) didn’t like it. More howling, foot stomping, and the like. Then he got to the nub of the matter: While we apparently had been successful, and his chest was practically bursting with pride, he did have one deep regret, that we hadn’t completed the Bomb in time to use against the Germans. That really brought down the house.

This had to be the most fascinating, to say nothing about being the most historic, speech I’ve ever heard. Apart from those who were there that night, I don’t recall ever meeting anyone who had ever heard of it. There’s an explanation for this that I won’t bother to go into here because that’s not what I’m writing about. That’s a matter for a good investigative reporter with an historic bent to go into, and maybe get himself a Pulitzer award.

His theoretical prediction of black holes was by far his greatest scientific achievement, fundamental to the modern development of relativistic astrophysics, and yet he never showed the slightest interest in following it up. So far as I can tell, he never wanted to know whether black holes actually existed. ...We know that the Oppenheimer-Snyder calculation is correct and describes what happens to massive stars at the end of their lives. It explains why black holes are abundant, and incidentally confirms the truth of Einstein's theory of general relativity. And still, Robert Oppenheimer was not interested. ...How could he have remained blind to his greatest discovery? ...Perhaps if the Oppenheimer-Snyder calculation had not happened to coincide with the Bohr-Wheeler theory of nuclear fission and with the outbreak of World War II, Robert would have paid more attention to it.

In later years I found a key to the character of Robert by comparing him with Lawrence of Arabia. Lawrence was in many ways like Robert, a scholar who came to greatness through war, a charismatic leader, and a gifted writer, who failed to readjust happily to peacetime existence after the war, and was accused with some justice of occasional untruthfulness.

Freeman Dyson, The Scientist As Rebel (2006)

His flaw was restlessness, an inborn inability to be idle. Intervals of idleness are probably essential to creative work on the highest level. Shakespeare, we are told was habitually idle between plays.

Freeman Dyson, The Scientist As Rebel (2006)

Robert was well aware of his own weakness. In later life he never spoke of himself directly, but he occasionally expressed his inner thoughts obliquely by quoting poetry. Especially from George Herbert, his favorite poet.

He was the genius of the nuclear weapons age and also the walking, talking conscience of science and civilisation; most of the great questions surrounding him as a person were the greatest questions of that time.
He was born into an intellectual New York Jewish family and as a young man experienced the revolution in theoretical physics in the 1920s at first hand in Europe, before settling in California and building a world-class research centre there. Though he had no record as a manager, when war came he was chosen as the Manhattan Project's chief scientist and his inspirational leadership saw it through to success.
Peace found him a national hero and a powerful voice in Washington, but he was also increasingly anxious about the drift into Cold War. These qualms made him enemies, so his pre-war left-wing past was dredged up and, at those 1954 hearings, he was subjected to what one observer called a "dry crucifixion". … Not a shred of credible evidence was ever produced to suggest that the man was disloyal, still less that he was a spy. The worst that could be proved against him was one or two lapses of judgement in dealings with left-wing friends in the early years of the war — piffling faults, as Isidor Rabi pointed out, when set beside his achievements.
So demented were his enemies that, even after what they described as his "unfrocking" — the official decision that he did indeed pose a risk to national security — they insisted he was on the brink of defecting to the Soviet Union and so must continue to be followed and bugged wherever he went.